okex3 withdraw trade_pwd precedence fix ccxt#6374

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README.md / social, link to gitter

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return an int from php milliseconds not a string

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Exchange.js keepAlive in Chrome fix ccxt#6368

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bittrex v2 endpoints

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1.21.53

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bitstamp, bithumb safeStringLower edits

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more to Manual.md ccxt#6364

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1.21.50

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Manual.md added more clarifications on TICK_SIZE ccxt#6364

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